Field of the Invention
The present invention relates to a manufacturing method of a power-module substrate for a semiconductor device controlling a large electric current and high voltage.
Description of the Related Art
Conventionally, it is known that a power-module substrate has a structure in which a circuit plate is bonded with laminating on one surface of a ceramic substrate and a heat-radiation plate is bonded with laminating on the other surface of the ceramic substrate. The power-module substrate is provided as a power module by soldering electronic components such as a semiconductor chip (a power element) and the like on the circuit plate and bonding a heat sink on the heat-radiation plate.
In such power-module substrates, for example, there is technology described in Patent Document 1 and Patent Document 2 as methods of bonding metal plates to be the circuit plate or the heat-radiation plate on the ceramic substrate by laminating.
Patent Document 1 discloses steps in which: adjusting a copper-circuit assembly in a state in which circuit elements are connected by thin bridge portions; printing bonding material such as Ag—Cu—Ti or the like including active metals such as Ti on a ceramic substrate in a pattern of the copper-circuit assembly; bonding the copper-circuit assembly and the ceramic substrate by heating with laminating; and then removing the bridge portions by an etching process.
Patent Document 2 discloses a method of manufacturing power-module substrates, including steps of: laminating and bonding a ceramic mother-plate and a metal plate with interposing a brazing foil; forming circuit patterns by etching the metal plate; forming grooves between the circuit patterns on the ceramic mother-plate; and dividing the ceramic mother-plate along the grooves.